Hi, the popups show the file name or URL where the virus was found (not only virus name, like Win64: Sirefef-A [Trj] and Win32: Sirefef-AQ ). Avast does not display popups for items already in the Chest, so you don't have to worry about deleting the contents of the chest - this is probably not your problem, the virus is.
What is the filenames/URLs you are being warned on?
Edit: you might also post screenshots of the warnings, if unsure what is the filename on the dialog. It will help virus removal specialists here.